Apparently this nylock nut had spontaneously worked its way off the bolt. The bolt is a custom machined part, and had backed out slightly but not enough to protrude from its deeply recessed hole in the cast fitting. All of this is original factory-installed hardware, never disassembled, and the nylock nut had not been reused. Evidently they can work loose in normal glider set up, break down, and flight. If the bolt were to back out the rest of the way in flight, a parachute ride would almost certainly follow.
Moyes glider owners might review their pre-flight checklists to be sure this item is covered. This is also a reminder to all of us that a careful pre-flight is a mighty good idea, even if it only finds one small problem like this every ten years.
